Simplify and refactor property

[timhall]

Previously, name was required as key to store property on internal __properties object and ended up being added boilerplate for every property that repeated the prototype key. Since this functionality is internal, the name isn't exposed and a unique id can be used instead which can then be used to determine the name, if necessary. To account for functions as default_value, type: 'Function' has been added, but it could affect directly set values. Instead, type has been removed, default_value is always evaluated if it's a function, and functions as default_value should be wrapped in a function. Finally prop_key is no longer available (__properties is always used).

Before:

a: property('a', {
  default_value: function defaultFn() {},
  type: 'Function'
}),
b: property('b')

After:

a: property({
  default_value: function() { return defaultFn() {} }
}),
b: property()

Changes:

• name: deprecated and will be removed in next version
• type: removed, must wrap function default_value
• prop_key: removed, always __properties